Geographic Range

Incan shrew opossums (Lestoros inca) are found in the Andes Mountains in Peru and Bolivia. They have been found near the headwaters of Rio Alto Madre de Dios, Rio Marcapata, and Rio Inamberi, as well as in departmento Las Paz, Bolivia. (Myers and Patton, 2008; Patterson and Solari, 2008)

Habitat

It has been suggested that this species prefers environments that are somewhat less wet than the other members of family Caenolestidae. However, they have been trapped in a variety of wet mossy areas, as well as drier scrub environments. Incan shrew opossums are found in montane environments with low trees, bushes and grasses, often in cloud or elfin forests. They have been found in elevations ranging from 1,800 to 3,600 meters. (Kirsch and Waller, 1979; Myers and Patton, 2008; Patterson and Solari, 2008)

Physical Description

Incan shrew opossums are marsupials. They are somewhat shrew-like in appearance and have elongated faces. They are the only members of the genus Lestoros, but are very similar in appearance to genus Caenolestes; however, Incan shrew opossums have smaller upper canines. Incan shrew opossums have thick, medium length, dark gray fur. They have curved ears, small eyes and long hind feet. These animals have whiskers on their chin, side of their nose and their forelimbs. Their total body length is approximately 90 to 120 mm, including a tail length of 105 to 135 mm, approximately the same length as their body. Incan shrew opossums weigh between 20 to 35 grams. (Kirsch and Waller, 1979; Myers and Patton, 2008)

In general, members of family Caenolestidae can be distinguished from other marsupial groups by their unique dentition. They have a reduced number of incisors and their lower middle incisors are large and have a forward slope. The dental formula for genus Caenolestes is: I 4/3, C 1/1, P 3/3, M 4/4, 46 teeth total. While their tail is not prehensile, it is used for support while they climb and for balance. Shrew opossums have short robust limbs, each containing 5 digits; their middle 3 digits are shorter than the outside two. Their humeri are extremely heavy; their femurs are relatively slender in comparison. Members of family Caenolestidae have unusual lip flaps, which may function as a method of preventing debris from interfering with their whiskers or it may help prevent ingestion of unwanted debris. Similar to other marsupials, Caenolestid females have 2 uteri and 2 vaginas. Members of genus Caenolestes lack a pouch but do have 4 mammae, 2 on either side of their abdomen. Caenolestids are sexually dimorphic, with adult males larger than adult females. (Albuja and Patterson, 1996; Lee and Cockburn, 1985; O'Connell, 2006; Osgood and Herrick, 1921; Tirira, 2007)

Common shrew opossums (Caenolestes obscurus), another member of family Caenolestidae, show evidence of a low metabolic rate, based on their body temperature (35.4° C), their body weight (about 40 g), their cool habitat and their thick fur coat. This species shows no evidence of entering torpor. (McNab, 1978)

Reproduction

There is currently little information available regarding the mating system of Incan shrew opossums.

Female Incan shrew opossums lack a marsupium; however, immature individuals may have an undeveloped fold of skin that they lose before reaching maturity. Females have 4 mammae available for their young to nurse. Evidence suggests that Caenolestid females have the same number of ova as mammae, unlike family Didelphidae. In support of that notion, a female was found pregnant with 3 embryos, 2 in the right uterus and 1 in the left. These animals likely have one annual breeding season from February to August. (O'Connell, 2006; Osgood and Herrick, 1921; Tirira, 2007; Tyndale-Biscoe and Renfree, 1987)

Home Range

There is currently no information available about the home range of Incan shrew opossums.

Communication and Perception

Members of family Caenolestidae have very small eyes and poor eyesight. Incan shrew opossums have tactile whiskers on their chin, the side of their nose and their forelimbs. Their unusual lip flaps have the hypothesized function of clearing debris from their sensitive vibrissae, but they may merely function as a method of preventing the ingestion of unwanted debris. Their somewhat primitive brains have enlarged olfactory bulbs, which could indicate an enhanced sense of smell. When they are startled they attempt to hide and they hiss when cornered. Caenolestids are not noted for frequent production of sound, however, captive individuals may make several sounds including whistles, bird-like screams, rat-like squeaks and drawing air through their incisors. (Hume, 1982; Kirsch and Waller, 1979; Myers and Patton, 2008; O'Connell, 2006; Vaughan, et al., 2011)

Food Habits

Members of genus Caenolestes are opportunistic feeders. Their stomach contents indicate that they are primarily insectivores. Ingested invertebrates include beetles, crickets, butterfly larvae, centipedes, grasshoppers, spiders, and earthworms. A smaller proportion of their diet is composed of vegetation, fruit and small vertebrates including juvenile mice. They forage for food in moss and leaf litter. When they find a food item, they manipulate and consume it with their forepaws, from a semi-seated position. As Caenolestids shear their food with their incisors, they produce a clicking sound. (Barkley and Whitaker, 1984; Timm and Patterson, 2008; Tirira, 2007)

Economic Importance for Humans: Positive

Due to their human-inaccessible habitat, there has been very little study of these animals. Likewise, there has been very little interaction between human and shrew opossum populations. They may, however, serve as a control of insect populations. (Kirsch and Waller, 1979)

Economic Importance for Humans: Negative

There are no known negative effects of Incan shrew opossums on human populations.

Conservation Status

Incan shrew opossums are currently plentiful in protected areas and are listed as a species of least concern on the IUCN Red List of threatened species. (Patterson and Solari, 2008)

Contributors

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Albuja, L., B. Patterson. 1996. A new species of northern shrew-opossum (Paucituberculata:Caenolestidae) from the Cordillera del Condor, Ecuador. Journal of Mammalogy, 77:1: 41-53.

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This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.